Optical fiber is now well known and widely used as a transmission medium in the telecommunications field. Lengths of fiber may be joined together by e.g. splicing for various reasons, e.g. to span a certain distance, or to connect e.g. a fiber leading from the core network and a fiber of the access network. Spliced fiber are very fragile at the splice point, and are typically protected from stress and damage by placing the spliced sections in a splice case or container.
Often the container takes the form of a tray, which in addition to protecting one or more splices, usually further serves to store (excess) lengths of fiber. An optical fiber splice closure or enclosure (also known as a joint) allows for a number of splice trays to be deployed in a relatively small area. In a typical configuration within a closure, the trays are stacked together so that in a stored position the tray faces or bases are in or almost in contact with each other. This minimizes the space envelope occupied by the splice closure, which is a boon in an environment such as within a footway box or a street cabinet, which is an increasingly crowded space, especially with the movement of bringing fiber within the “last mile” ever closer to end-customers in the push to Fiber to the Home or such points within the access network (FTTx).
As expected, this push of fiber outwards to end-customers will dramatically increase the number of connections required especially in the access network. While it is possible to deploy another splice enclosure, the limited and decreasing space within the footway box or cabinet makes it desirable to increase the capacity of optical fiber splice enclosures used particularly in distribution points. It would be even more desirable if the solution did not involve any significant change to the current configurations and space envelopes of fiber splice closure joint. It would also be advantageous to make few changes to current, mature techniques of splicing and storing optical fiber using splice trays. Keeping current sizes and practices would avoid or reduce the need to reconfigure spaces and to learn new methods.
An example of a splice closure of the type referred to above is the FIST-GCO2-F sealed enclosure from Tyco Electronics Raychem N.V. of Belgium, whose website is located at www.tycoelectronics.com. This unit has a single element splicing capacity of 96 fibers on 8 trays, or 144 fibers on 12 trays. In this enclosure, trays are pivotably attached in a row to the main unit along a linear backplane which serves as a spine, as illustrated in FIG. 1 and discussed further below. This allows for the functional faces of the trays to be exposed for access when they need to be worked upon, and for them to be stored away in a stack, as will be discussed further below. The height or length of the backplane is a chief determinant of the capacity of the enclosure in that it puts a limit on the number of splice trays that may be contained in the joint.
Various other tray arrangements within such enclosures are known in the prior art. The storage enclosure of GB 2316496A describes a configuration in which a tray is hinged not to a backplane, but to an adjacent tray in a series. All the hinged points are located at substantially the same location on each tray, so the trays are (similar to the Tyco enclosure discussed above) attached to each other in a row. A variation of this configuration is described in U.S. Pat. No. 5,835,657, in which trays are also attached to adjacent trays in a row. Attaching trays to each other in a series in the ways described in these two pieces of prior art wherein the attachment points are disposed in a row, are therefore functionally identical or very similar to attaching trays along a backplane or central spine. Yet another arrangement is described in EP 1333303 comprising a pair of splice trays, which are nested within each other. The outer tray is attached to the backplane, and the inner tray is attached to the outer tray in a way so that both pivot in the same direction to allow access to the working surfaces of the trays.
A problem suffered by prior art tray enclosures stacked vertically along a linear backplane is that to access a particular tray, not all the trays are easily accessible, especially the ones further removed from a user's reach or sight e.g. the highest or lowest trays in the stack. Furthermore, access to the desired tray requires that those trays which are not being worked, to be stowed or secured out of the way, which requires additional components or elements, and usually involves at least one additional step in the splicing process. Because of the sheer scale of a FTTx undertaking, these all add up to significant amounts of cost and time. It would be desirable to reduce and to simplify the process of providing splices and to save time and cost in doing so.